Stroke is a leading cause of disability in the United States, and mental illness affects tens of millions of Americans each year. New research finds a link between the two, as psychiatric illness is found to raise the risk of stroke.

A new study suggests those who have mental health problems may also be at an increased risk of stroke.

The American Heart Association (AHA) estimate that almost 800,000 Americans have a stroke each year, and almost 130,000 people die from it.

Mental disorders also affect a large number of the U.S. population. According to the latest statistics from the National Institute of Mental Health (NIMH), over 43 million American adults aged 18 and above have had a form of mental illness in the past year. This represents nearly 18 percent of all American adults.

The study was led by Jonah P. Zuflacht, a fourth-year medical student at Columbia University’s College of Physicians and Surgeons in New York, and the findings were presented at the American Stroke Association’s International Stroke Conference 2017.

The study’s lead author explains the motivation behind the research.

“Based on my clinical experience in the hospital, I have noticed that many patients believe that stress for whatever reason – work, family, work-life balance – contributed to their stroke,” Zuflacht says. “But the data to support a connection between stress and stroke is limited and often relies on a patient’s subjective recall of distress, which can bias results.”

Stroke almost 3.5 times more likely in people with psychiatric disorders

The researchers examined data from the Healthcare Cost and Utilization Project (HCUP) database for California. The HCUP is the most comprehensive hospital care database in the U.S., and it includes information on hospital visits, in-patient stays, as well as ambulatory services.

Zuflacht and colleagues found a total of 52,068 individuals who received hospital care for stroke between 2007 and 2009. Of these, 3,337 people also received care for depression, anxiety, PTSD, or other mental health issues.

The team applied a case-crossover analysis to examine if psychiatric disorders led to an increase in the risk of stroke within several time periods.

They found that people who had visited the hospital for a mental health concern were 3.48 times more likely to have a stroke within 15 days of their visit, and 3.11 times more likely within 30 days.

The odds of a stroke decreased as the time period increased, although they remained significantly high for psychiatric patients for up to a year. The risk was 2.41 times higher within 90 days of the hospital visit, 2.23 times higher within 180 days, and 2.61 times higher within 360 days of their psychiatry-related hospital visit.

Although this is an observational study and the authors did not set out to establish causality, lead author Zuflacht speculates on possible explanations for the results. Psychologic distress, he explains, may cause the brain to react with a “fight-or-flight” response – the body’s natural reaction to a state of danger. This, in turn, triggers high blood pressure, which is the leading risk factor for stroke.

Psychiatric disorders may also lead to changes within the cell, causing inflammation and oxidative stress, which are also believed to contribute to the risk of stroke, Zuflacht explains.

The study’s lead author also comments on the significance of the study.

“Healthcare professionals should listen to their patients for symptoms of psychiatric illness, especially in those who may be at increased risk of stroke. A patient with high blood pressure, high cholesterol, and 6 months of depressive symptoms should raise concerns regarding possible stroke risk.”

Dr. Jonah P. Zuflacht

Some of the limitations of the study include the missing information on what specific psychiatric condition each individual had. Such detailed information might have shed some light on which mental illnesses correlated more strongly with stroke. Additionally, the team did not include any information on outpatients with psychiatric conditions.